Spectropolarimetry of the Type Ia SN 2019ein rules out significant global asphericity of the ejecta

Abstract

Detailed spectropolarimetric studies may hold the key to probing the explosion mechanisms and the progenitor scenarios of Type Ia supernovae (SNe Ia). We present multi-epoch spectropolarimetry and imaging polarimetry of SN 2019ein, an SN Ia showing high expansion velocities at early phases. The spectropolarimetry sequence spans from ∼ −11 to +10 days relative to peak brightness in the 𝐵-band. We find that the level of the continuum polarization of SN 2019ein, after subtracting estimated interstellar polarization, is in the range 0.0-0.3%, typical for SNe Ia. The polarization position angle remains roughly constant before and after the SN light-curve peak, implying that the inner regions share the same axisymmetry as the outer layers. We observe high polarization (∼ 1%) across both the Si 𝜆6355 and Ca near-infrared triplet features. These two lines also display complex polarization modulations. The spectropolarimetric properties of SN 2019ein rule out a significant departure from spherical symmetry of the ejecta for up to a month after the explosion. These observations disfavour merger-induced and double-detonation models for SN 2019ein. The imaging polarimetry shows weak evidence for a modest increase in polarization after ∼ 20 days since the 𝐵-band maximum. If this rise is real and is observed in other SNe Ia at similar phases, we may have seen, for the first time, an aspherical interior similar to what has been previously observed for SNe IIP. Future polarization observations of SNe Ia extending to post-peak epochs will help to examine the inner structure of the explosion.

Common Envelope to Explosion Delay time Distribution (CEEDTD) of Type Ia Supernovae

“…There is neither consensus on the main scenario that triggers white dwarfs (WDs) to ignite thermonuclear explosions as type Ia supernovae (SNe Ia), nor on the classification of the different SN Ia scenarios (e.g., Livio & Mazzali 2018;Wang 2018;Jha et al 2019;Ruiz-Lapuente 2019;Soker 2019a;Ruiter 2020 for very recent reviews). As most recent studies continue to explore all scenarios (e.g., Livneh & Katz 2020;Pan 2020;Wu et al 2020;Ablimit 2021;Blondin et al 2021;Chandra et al 2021;Clark et al 2021;Ferrand et al 2021;Liu et al 2021;Livneh & Katz 2021;Meng & Luo 2021;Michaely 2021;Patra et al 2021;Zeng et al 2021), I briefly review (in alphabetical order) the six binary SN Ia scenarios according to Soker (2019a), where one can find more details. I will not discuss single star scenarios (e.g., Clavelli 2019; Antoniadis et al 2020).…”

Common envelope to explosion delay time of Type Ia supernovae

“…Pan 2020; Wu et al 2020;Blondin et al 2021;Clark et al 2021;Ferrand et al 2021;Livneh & Katz 2020;Ablimit 2021;Livneh & Katz 2021;Liu et al 2021;Meng & Luo 2021;Michaely 2021;Zeng et al 2021;Chandra et al 2021;Patra et al 2021), I briefly review (by alphabetical order) the six binary SN Ia scenarios according to Soker (2019a), where one can find more details. I will not discuss single star scenarios (e.g., Clavelli 2019;Antoniadis et al 2020).…”